This storm glass is the same size and shape as our 6" Galileo Thermometers, and they make an attractive pair on the windowsill. 6" Tall The storm glass was popularised by Admiral Robert Fitzroy after his historic voyage on the HMS Beagle. How the Storm Glass works is still a mystery, but it is believed that electromagnetic changes in weather patterns activate the crystals inside (sealed glass chamber fill with crystals when air pressure decreases). This is a gorgeous decorative gift idea for the adult who has everything or someone who finds meteorology fascinating. How to read: A: Clear Liquid Bright and clear weather B: Cloudy Liquid Sometimes with small stars and crystals at the top. Cloudy weather and often predicts thunderstorms and rain. C: Small Stars in Liquid Humid or foggy weather D: Large Flaky Crystals Cloudy skies, snow in winter. E: Threads of Crystals At The Top Winy Weather F: Crystals At The Bottom, Frost may be coming.